Method of manufacturing split prongs for loose leaf binders



y 1961 K. G. KARLSSON 2,990,611

METHOD OF MANUFACTURING SPLIT PRONGS FOR LOOSE LEAF BINDERS Filed May 5, 1958 #7940 7C F/Q4 v INVENTOR. W a.rL Guscav KarLsson I United States Patent 2,990,611 METHOD OF MANUFACTURING SPLIT PRONGS FOR LOOSE LEAF BINDERS Karl Gustav Karlsson, Norrvikeu, Sweden, assignor to Aktiebolaget Galco, Stockholm, Sweden, a corporation of Sweden Filed May 5, 1958, Ser. No. 732,936 Claims priority, application Canada July 19, 1957 1 Claim. (Cl. 29531) This invention relates to the manufacture of prongs of the split prong type for loose leaf binders. Such prongs are of the right-hand and left-hand types secured to opposite sides of the back of the binder so as to engage the punched apertures in the filler sheets. Each prong should be substantially half oval or half circular in cross-section such that the flat sides of appertaining prongs are facing each other. In order to prevent the filler sheets from being damaged by the prongs, the prongs should be straight and have a face as flat as possible. It has proved difficult to manufacture in an inexpensive manner prongs which meet the above requirement if the prongs are desired to have a curved shape.

The object of the invention is a method of manufacturing split prongs which are inexpensive and accurate in service. The method according to the invention consists in bending a round wire blank to an arcuate shape and then moulding the same by application of pressure in a die to a substantially half round cross-sectional form.

The invention is described more closely hereinbelow with reference to the annexed drawing in which FIG. 1 is a diagrammatic view of a binder having split prongs, viewed in the longitudinal direction of the back of the binder, whereas FIGS. 2 to illustrate different steps of manufacture of a prong.

Referring to FIG. 1, numerals 2 and 3 denote the two halves of the back of a binder, said halves being connected to each other by means of a hinge pin 1. The sides or covers 4 and 5 of the binder are pivotally connected with the back 2, 3 by means of hinge pins 14 and 15 respectively. Numerals 6 and 7 indicate two opposed cooperating prongs which are substantially half oval or half round in cross-section. There is a row of such cooperating prongs arranged along the back of the binder.

The prongs are manufactured from an iron-wire stock which is cut into blanks of proper length. FIG. 2 illustrates such a blank 7a which is circular in cross-section as shown in FIG. 2a. One end of the blank is pointed, such as at 9, for instance by a turning or punching operation. The blank is then bent such as to assume a curved or arcuate shape, as shown in FIG. 3. This step of the manufacture may be performed by means of two press dies which are movable relative each other as indicated by arrows. The end of the blank opposite the point 9 is left in its initial straight form, this end 2,990,611 Patented July 4, 1961 "ice being later on formed to a fastening part for the prong. The bent portion 7b is still circular in cross-section, as shown in FIG. 3a.

The product thus obtained is then placed into a die including a sunk portion having the same radius of curvature as said product and is then subjected to pressure such as to obtain, by compression of the material, the cross-sectional shape shown in FIG. 4a, said shape being half round and having a flat side 11. During the lastnamed operation, the width of the member 7c has been increased to a value somewhat greater than the diameter of the initial blank 7a. At the same time the fastening end 10 is given a substantially rectangular shape and a shoulder 12, as will appear also from FIG. 5 which is a top view of the finished prong according to FIG. 4.

Due to the method of manufacture described above, the prongs are given the accurate desired shape having the side 11 as flat or plane as possible so as to ensure perfect registry of opposed prongs. It will be obvious that two registering prongs of each pair are mirror reflections of each other.

The end portion 10 is used to rivet the prong to the back half 2 or 3, as shown in FIG. 1, the shoulder 12 as well as the end 10 being deformed by means of suitable tools.

The prongs may be fastened to metal strips which are then secured to the back halves 2 and 3, respectively.

Preferably, all of the prongs (two, three or more) for one side of the binder are riveted simultaneously to the back or metal strip.

What I claim is:

The method of manufacturing prongs of the halfround split type for loose-leaf binders which comprises the steps of pointing one end of a linear blank of round wire, bending the portion of the blank adjacent the pointed end to an arcuate shape while maintaining the other end of the blank in its original straight condition, and then moulding the pointed end of the blank in a die by the application of pressure in a direction perpendicular to the plane of bending to a substantially half-round cross-sectional configuration and simultaneously forming the other end of the blank to a rectangular cross-sectional configuration to form a fastening part of the prong.

References Cited in the file of this patent UNITED STATES PATENTS 768,615 Moore Aug. 30, 1904 2,154,009 Priest Apr. 11, 1939 2,172,909 Johnson Sept. 12, 1939 2,343,933 Saul Mar. 14, 1944 2,616,314 Zeller Nov. 4, 1952 FOREIGN PATENTS 231,598 Great Britain Apr. 9. 1925 

